I propose we add "Pending ..." node (in places of loading content) while ajax tree node content is being loaded. This will create effect, that content loads faster. After content is loaded "Pending ..." node will be replaced with actual content.

We can't measure how long data is loaded to show "Loading" or not, because
we need to show "Loading" before data is loaded. But, when no data will be
returned, then "Loading" will be added and removed and tree will jump.

We are getting delays, when site is viewed from different country. Loading
indicator is a lot faster to implement then to perform full scale
application performance improvements. And it will give us nice effect (see
in Zend Studio 7 for Eclipse for yourself).